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The aircraft were flown by Deutsche Luft Hansa on transatlantic routes between 1937 and 1939, predominantly between Bathurst, The Gambia and Natal, Brazil. Catapult-launched from an aircraft tender they were able to transport 500 kg of mail over a distance of up to 5,000 km.

On the outbreak of World War II, the planes were transferred to the Luftwaffe and used for transport, reconnaissance and minesweeping work over the Baltic Sea. They were not particularly suited for military use.

Ha 139 was designed to transport mail and cargo over long distances. First of all, these were the regions located in the northern and southern Atlantic, where the German airline Lufthansa AG was engaged in this kind of transportation. Three aircraft named Nordmeer, Nordwind and "Nordstern" regularly flew on the following routes:
Horta, Azores, - New York - North Atlantic, 3850 km;
Bathurst, New Brunswick, Canada - Recife, Brazil - South Atlantic, 3100 km.

The German airline Lufthansa AG has issued an order for a floatplane capable of flying with a payload of 400 kg over distances of 5,000 km at an economic speed of 250 km/h. At full takeoff weight, it was supposed to use launch boosters. Take-off from the surface of the water and the corresponding characteristics were only possible with a take-off weight with a fuel supply sufficient for a flight of only 1000 km.

To meet these requirements, it was necessary to create an aircraft with the smallest possible dimensions. As a result, the Ha 139 was designed as a floatplane with a number of limitations regarding its performance while on the water surface. The fuselage was sized to carry 500 kg of mail. For this aircraft, the most economical diesel engines of the Junkers Jumo 205 type with a takeoff power of 600 hp were chosen. , consisting of four motors, and demanded that due attention be paid to the aerodynamic perfection of the aircraft design. In order to prevent splashes from entering the cockpit and onto the tail unit, the middle section of the wing received a kink, slightly raising the fuselage above the floats. This technical solution did not create difficulties in the production of a tubular spar of the wing. So there was a four-engine low-wing aircraft Ha 139 with two floats with a volume of 12,500 liters each, which provided take-off with a catapult with a full take-off weight and take-off from the water surface with a reduced flight weight.

The kink of the wing panels was slightly changed, the wingspan was increased, the fuselage was slightly raised. Improved aerodynamics provided increased flight performance and increased flight range.

The wing had a constant chord length throughout its span. The wing consisted of a center section attached to the fuselage with a pronounced negative transverse V and a span of 16 meters and two consoles. On the leading edge of the wing, as was customary, four Jumo 205 engines were attached.

The cross section of the fuselage had an oval shape. Rescue equipment was installed in front of the aircraft fuselage. Behind the bow was the cockpit of a crew of four: two pilots, a flight engineer and a navigator. The flight engineer's seat with a set of instrumentation, levers and switches was located on the starboard side behind the pilots' seats. On the left side there was a navigator's seat with navigation and equipment, communications equipment and a direction finder. Behind the one-piece tubular spar of the wing passing through the fuselage, there was a luggage compartment with a volume of 7.5 m³. In the luggage compartment there was a place for the fifth crew member and a toilet.

Vertical two-keel plumage, the keels of which were located in the jets of air thrown by the propellers of the internal engines of the power plant. Water splashes on the tail, as a rule, did not fall, since it was located high enough above the fuselage. The keels and stabilizers had metal sheathing, the rudders and elevators had fabric sheathing. The steering wheels were equipped with trim tabs. Four landing flaps were hydraulically controlled on the inner section of the wings.

The welded tubular spar of the center section of the wing, which had a span of 16 meters, was made of Aero 70 sheet steel of various thicknesses. This spar perceived bending and twisting loads. In addition, two elements were attached to the spar by welding, through which the loads from the catapult were transferred. Also, along the entire length of the wing spar, there were four large fuel tanks and one small reserve tank with a total capacity of 6500 liters. The tanks were separated from each other by removable partitions. Flanges were also attached to the spar, with the help of which the wing was attached to the fuselage, as well as engine frames, mounting rods of the control system. The floats were attached to the wing spar with steel flanges welded to it, equipped with fittings (Rohrstutzen).

The wing ribs were riveted from U-shaped profiles and connected by a wing spar using a steel angle profile. The connection of the ribs and the spar was also performed using riveting. The center section of the wing was covered with sheets of metal, the wing consoles were covered with canvas.

The fuselage of the aircraft had a monocoque structure, in which a large number of spars were additionally reinforced by a working skin that perceived longitudinal loads. Frames installed across the fuselage, with the exception of two box-shaped frames installed in the midsection at the intersection of the wing spar, were a construction of an angled profile.

The floats with a volume of 12,500 liters each were separated by sealed longitudinal and transverse bulkheads. Access to the inside of the floats was provided in the bow and stern with the help of bulkhead clinkers (Schottüren). The floats were connected to the wing by means of steel flanges provided with fittings. These cantilever mounts were covered with fairings.

The engines were attached/suspended to the fender at four points using new box-shaped motor frames. On the one hand, the engine was mounted on elastic elements, on the other hand, the fasteners were similar to stands. Mounting the motors on parallel spring-loaded elements in this manner worked very well, as the motors ran without much vibration.

The engine radiators were mounted on the lower surface of the wing outside the airflow from the propellers. The radiators were semi-recessed in the channels. Adjustment of the air flow removed from the radiators was carried out using adjustable outlet flaps.

The first Ha.139-V1 (factory No.181, D-AMIE) first flew in the fall of 1936. and was transferred to Lufthansa in March 1937. under the designation Ha.139a "Nordmeer". It was followed in June by the Ha.139-V2 (#182, D-AJEY), named Ha.139a Nordwind by Lufthansa. These aircraft were used from the Friesenland and Schwabenland aircraft and made seven flights between Horta in the Azores and New York from August to the end of November 1937. The average speed in the western direction was 228 km/h, in the east - 250 km/h.

Both A-series aircraft were equipped with four Junkers-205D diesel engines with Junkers-Hamilton three-blade variable-pitch propellers. Radiators behind adjustable flaps were placed in pairs on the float racks. The tubular central spar contained five tanks with a total capacity of 6000 liters of fuel. Mooring devices were located in the bow. The cockpit allowed two pilots to be placed side by side. Immediately behind them sat the flight engineer on the right and the radio operator on the left. The compartment for cargo and mail was located behind the spar and was inaccessible to the crew.

Low directional stability, due to small round spaced tail washers, required an increase in the area of ​​​​the rudders. Poor cooling of the engines led to the installation of an additional air intake on top of the engine cowl. The radiators in the racks were removed due to corrosion from salt water that fell during takeoff and landing and were moved under the engines under the wing.

In the spring of 1938 The two A-series aircraft were joined by the B-series prototype, the Ha.139-VЗ (#217, D-АSTA), which entered Lufthansa under the designation Ha.139b Nordstern. The engines remained Jumo-205С, but the weight increased - empty from 10370kg to 10950kg, takeoff from 16990kg to 17565kg. The dimensions also increased: span up to 29.5 m (on H.139a - 27 m), length 19.65 (19.51) m; height - 4.8 (4.6) m; wing area - 126 (113) sq.m. The engine nacelles were somewhat lowered, and the plumage washers were enlarged.

Between July 21 and October 19, 1938. Ha.139-V3 made several flights between Horta and New York along the North Atlantic route, flying together with V1 and V2 597 hours. Subsequently, these three aircraft flew to Germany, Italy, Brazil, operated in the southern sector of the Atlantic until the start of World War II.

With the outbreak of hostilities, Lufthansa had little opportunity to use the Ha.139. It was decided to convert them into long-range naval reconnaissance aircraft. Ha.139-V3 was returned to Wenzendorf for an experimental upgrade. The nose part was lengthened and equipped with an observer's place. The MG-15 machine gun was mounted in the nose on the Ikaria installation. The second MG-15 was used by the radio operator to fire through the hatch on the cabin roof. Another pair of machine guns was installed in the "lenses" on the sides of the fuselage. Radio and navigation equipment was reinforced, takeoff weight increased to 19000kg. The aircraft received the designation Ha.139b/Umbay (reconstructed). The modified aircraft made its first flight on January 19, 1940. in the Baltic after launch from the Friesenland catapult. The crew consisted of Lieutenant Count Shaka and Fleet Captain Schuster.

Ha.139b / Umbay was after testing delivered to the 1st squadron of the 406th coastal aviation regiment. This unit was mainly equipped with Do.18 flying boats, which were reinforced with five Do.26s during the Norwegian operation. Aircraft 1./Ku.Fl.Gr.406 made reconnaissance and transport flights during the fighting in Norway. Ha.139b/Umbay conducted mainly weather reconnaissance in the Arctic sector. In the meantime, two Ha.139a were converted according to his model and also participated in the Norwegian operation as part of KG.zbv108 See, operating from Nordenej and delivering military equipment and other supplies to the Norwegian fjords for isolated parts of the Wehrmacht.

The lack of spare parts for Ha.139 limited their use, but in 1942. Ha.139b/Umbay was again modified into minesweeper Ha.139b/MS. A somewhat unusual magnetic winding went from the nose of the fuselage down to the floats, then up to the ends of the wings, and then to the plumage. There is no evidence that it was used in the squadrons of the mine-finder regiment. Most likely, again, due to a lack of spare parts, the aircraft was scrapped, like its predecessor.

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